1. Field of the Invention
The present invention relates to a quality of service (QoS) control layer structure and packet-based transmission control parameters for supporting QoS in a communication system. More particularly, the present invention relates to a method of generating packet-based transmission control parameters and a QoS control layer structure for providing high quality audio-video (AV) service by reflecting characteristics of AV data in the scheduling process.
2. Description of the Related Art
Parameters used for supporting quality of service (QoS) in a communication system specify application characteristics, delay time, a difference between transmission delay times, a priority level, and the like. Application characteristics represent information related to whether the application data is transmitted in real-time or using a fixed bandwidth. The delay time and the difference between the transmission delay times represent information related to the time period of data transmission. The priority level represents information related to transmission sequencing of data.
In conventional methods of supporting QoS in media access control (MAC) layers, transmission control parameters are designated individually for respective sessions that are managed by each application. Therefore, scheduling or a retransmission mechanism, or the like, is managed by the individual transmission control parameters of the respective session.
Meanwhile, data frames used for providing an audio-video (AV) service have different characteristics between each frame, contrary to general data frames, all of which have generally similar characteristics. Therefore, it is inefficient to use conventional general QoS management for AV service in which the respective sessions are managed separately. In addition, conventional systems statically determine transmission control parameters according to the characteristics of the sessions. Therefore, such conventional systems cannot accurately reflect the characteristics of the AV frames described above.
In particular, certain frames (for example, an I-frame (Intra-coded frame) and a B-frame (Bidirectional-coded frame)) within an MPEG-2 stream have different characteristics from each other, contrary to the general data frames, all of which have the same characteristic as described above. For providing AV service, data should be transmitted in real-time. For real-time transmission and to achieve QoS, the transmission delay time of the data and the difference between the transmission delay times of the data must be maintained. For this reason, the MPEG-2 data (frames) should be transmitted according to their characteristics.
However, in a conventional wireless communication system, MPEG-frames are transmitted according to scheduling in the MAC layer using QoS parameters defined for the respective sessions, in the same manner as a general data transmission. In such conventional wireless communication systems, because the characteristics of the MPEG-2 frames are not reflected in the scheduling of the MAC layer, it is very difficult to provide real-time AV service.